{"metadata":{"image":[],"title":"","description":""},"api":{"url":"","auth":"required","params":[],"results":{"codes":[]},"settings":""},"next":{"description":"","pages":[]},"title":"Context & Event Aggregator","type":"basic","slug":"example-context-and-event-aggregator","excerpt":"Using Node.js' EventEmitter to handle events","body":"[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"import {EventEmitter} from \\\"events\\\";\\nimport {task, TaskContext} from \\\"natron-core\\\";\",\n      \"language\": \"javascript\"\n    }\n  ]\n}\n[/block]\n## Creating a Custom Context\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"class CustomContext extends TaskContext {\\n\\n  log(opts, ...args) {\\n    let lvl = this.stack.length - 1;\\n    args.unshift(opts && opts.ico || \\\" \\\");\\n    if (lvl) {\\n      let indent = \\\" \\\".repeat(lvl * 2 - 1);\\n      args.unshift(indent);\\n    }\\n    return console.log(...args);\\n  }\\n}\",\n      \"language\": \"javascript\"\n    }\n  ]\n}\n[/block]\n## Listening for Events\n\n`start` ... `e = {task, context}`\n`finish` ... `e = {task, context, value}`\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"let ea = new EventEmitter();\\n\\nea.on(\\\"start\\\", (e) => {\\n  let {task, context} = e;\\n  let name = task.name || getAnonymousName(e);\\n  context.log({ico: \\\"⇢\\\"}, name);\\n});\\n\\nea.on(\\\"finish\\\", (e) => {\\n  let {task, context} = e;\\n  let name = task.name || getAnonymousName(e);\\n  context.log({ico: \\\"⇠\\\"}, name);\\n});\",\n      \"language\": \"javascript\"\n    }\n  ]\n}\n[/block]\n`getAnonymousName`\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"let un = new WeakMap();\\n\\nfunction getAnonymousName(e) {\\n  let name = un.get(e);\\n  if (!name) {\\n    name = `<task_${(Math.random() * 1e2)|0}>`;\\n    un.set(e, name);\\n  }\\n  return name;\\n}\",\n      \"language\": \"javascript\"\n    }\n  ]\n}\n[/block]\n## Defining Tasks\n\n`t`: `a => (a || b) => b`\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"function a(val, ico = \\\"a\\\") {\\n  if (val instanceof Array) {\\n    val = `[${val.join(\\\", \\\")}]`;\\n  }\\n  this.log({ico}, \\\"val\\\", \\\"=\\\", val);\\n  return `(${val}<${ico}>)`;\\n}\\n\\nfunction b(val) {\\n  return a.call(this, val, \\\"b\\\");\\n}\\n\\nlet t = task([a, [[a, b]], b], {\\n  name: \\\"ab-task\\\",\\n  options: {pipe: true},\\n});\",\n      \"language\": \"javascript\"\n    }\n  ]\n}\n[/block]\n## Run\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"let context = new CustomContext({\\n  args: [\\\"foo\\\"],\\n  eventAggregator: ea,\\n});\\n\\n(t.runWithContext(context)\\n  .then((val) => {\\n    console.log(\\\"val\\\", \\\"=\\\", val);\\n  })\\n);\",\n      \"language\": \"javascript\"\n    }\n  ]\n}\n[/block]\n## Output\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"⇢ ab-task\\n  ⇢ a\\n  a val = foo\\n  ⇠ a\\n  ⇢ <task_42>\\n    ⇢ a\\n    ⇢ b\\n    a val = (foo<a>)\\n    b val = (foo<a>)\\n    ⇠ a\\n    ⇠ b\\n  ⇠ <task_42>\\n  ⇢ b\\n  b val = [((foo<a>)<a>), ((foo<a>)<b>)]\\n  ⇠ b\\n⇠ ab-task\\nval = ([((foo<a>)<a>), ((foo<a>)<b>)]<b>)\",\n      \"language\": \"text\"\n    }\n  ]\n}\n[/block]","updates":[],"order":0,"isReference":false,"hidden":false,"sync_unique":"","link_url":"","link_external":false,"_id":"5651c8f4011c003500eca8c7","__v":15,"githubsync":"","user":"5617a0a4a410c90d00c612f4","category":{"sync":{"isSync":false,"url":""},"pages":["5651c8f4011c003500eca8c7","5657ad06a795770d00a2afb5"],"title":"Examples","slug":"examples","order":3,"from_sync":false,"reference":false,"_id":"5651c89a852cfb3500a69830","__v":2,"createdAt":"2015-11-22T13:52:26.932Z","version":"5619a39913874c0d007038e9","project":"5617a1f5a410c90d00c612f5"},"createdAt":"2015-11-22T13:53:56.976Z","version":{"version":"0.2","version_clean":"0.2.0","codename":"Orange Arrow","is_stable":true,"is_beta":true,"is_hidden":false,"is_deprecated":false,"categories":["5619a39a13874c0d007038ea","5619a39a13874c0d007038eb","5619a39a13874c0d007038ec","5619a39a13874c0d007038ed","5651062a3b4d113500ed22d1","5651c89a852cfb3500a69830","565505ad055aa40d006f0ca7","56c219d8d3199a0d00694be6"],"_id":"5619a39913874c0d007038e9","createdAt":"2015-10-10T23:47:37.777Z","project":"5617a1f5a410c90d00c612f5","__v":5,"releaseDate":"2015-10-10T23:47:37.777Z"},"project":"5617a1f5a410c90d00c612f5"}